1. Functional Background & Related Art
It is well known that the human accommodative system can be trained to improve its performance. The most considerable studies are mentioned in the “Borish's Clinical Refraction”, see reference [1] (herein all reference numbers are included into rectangular brackets, and a list of the references is placed at the end of the present description).
Marg [7] showed that steady-state accommodation could be varied easily by volitional control in the presence of a target and related blur feedback. These results were later confirmed and expanded by others [2, 3, 8].
Using an objective recording system, Randle and Murphy [9] showed that with repeated testing (every 3 waking hours for 7 days; 3 hours total per day) of dynamic accommodative ability (predictable step and sine inputs), performance improved considerably.
These results are consistent with a clinical study by Levine et al. [10], which showed that only a few minutes per day of testing accommodative facility with ±2.00 D flippers produced considerable improvement in overall responsivity in asymptomatic young adults. The lens flipper with plus lenses on one side, and the minus lenses are on the other, is shown in FIG. 1—Prior Art.
Several studies have demonstrated that it is also possible to train and improve accommodation in symptomatic patients manifesting slowed dynamics. The first study was that of Liu et al., [11] who treated three optometry students with symptoms related to focusing difficulties at near using standard vision training procedures, including jump focus, plus-and-minus lens flippers, and pencil push-ups [12]. Subjects trained themselves at home, for 20 minutes each day for 4.5 to 7 weeks, and objective measurements of dynamic accommodation were made each week.
Initially, these measurements showed prolongation of the time constant and latency of accommodation. During treatment, the patients exhibited significant reductions in these two parameters that correlated well with reduction of symptoms. Flipper rates increased and symptoms were either markedly diminished or no longer present at the termination of therapy.
These results clearly demonstrate that vision training in this small sample of young adult patients resulted in objective improvement of accommodative function. The reduction in time constant suggested revision and improvement in the neuromotor control program [13] leading to a more efficient, time-optimal response. This might involve greater synchronization of neural signals related to the improved blur information processing. The reduced latency also suggested more efficient signal processing of blur information.
Two years later, these results were reproduced in children [14]. The adult results were also later confirmed and extended by Bobier and Sivak [15] using a different objective recording technique (photorefraction). They found no regression of improvement 4.5 months after cessation of training. In addition, subjective (minus lens) and objective (i.e., visual-evoked-response amplitude) increases in the amplitude of accommodation were recorded during a 4-month course of vision training in one patient [16]. Lastly, the slope of the accommodative stimulus-response function showed improvement after 8 to 16 weeks of basic accommodative therapy in a group of college students. This normalization was maintained when patients were retested 6 to 9 months later.
Together, results of the foregoing studies clearly demonstrate that symptoms related to near focusing were correlated with the clinical accommodative lens flipper rate [17-20]. Furthermore, objectively determined improvement in accommodative dynamics was paralleled by similar changes (i.e., increased timed cycles) in accommodative lens flipper rate.
Thus, in the clinical environment, the lens flipper (“accommodative rock”) provides a simple, inexpensive, effective, and valid diagnostic and therapeutic indicator of overall accommodative dynamic ability. Combining this with careful static measures of accommodative amplitude (minus-lens technique or dynamic retinoscopy) and steady-state error of accommodation (i.e., near lag/lead, again using dynamic retinoscopy), practitioners can begin to obtain comprehensive static and dynamic clinical profiles of their patients' accommodative abilities [4, 21].
A few studies have shown that it is possible to train and improve accommodation in patients with other clinical conditions with verification using objective recording techniques or psychophysical test paradigms. In the area of amblyopia, Benjamin showed that both static accommodation and dynamic accommodation normalized after conventional vision therapy (part-time occlusion, eye-hand sensorimotor exercises, and lens flipper [22].
With regard to static accommodation, therapy resulted in reduced accommodative lag (and thus increased, more accurate response amplitude), reduced depth of focus, and increased accommodative amplitude [4, 5, 6, 23-26]. With respect to dynamic accommodation, therapy resulted in reduced latency, increased response amplitude (i.e., increased system gain), and more accurate accommodation, with less variability and improved response sustaining ability [22].
The amblyopia therapy improved neurosensory sensitivity and processing, as well as reduced the unsteady and eccentric fixation, all of which acted to improve overall static and dynamic accommodative function [22]. Similar findings were reported in a case of myasthenia gravis [27].
Also, one patient with congenital nystagmus achieved more accurate accommodation after eye movement auditory feedback therapy [28]. This probably resulted from reduced retinal image motion and therefore a higher contrast retinal image with more distinct edges to stimulate accommodation more effectively.
Since the effect of accommodative system training had been manifested, the training device, or apparatus, or other embodiment of accommodation training idea was brought to the fore.
The straightforward solution was to use the conventional procedures of accommodation measuring, along with the relevant equipment, for accommodative system training. The following tests are typically used for training the accommodative and vergence systems.
The representative procedure is the amplitude of accommodation measurement “push-up” or “pull away” test (Donder's Test). This test is destined to determine the maximum amount of accommodation that the eyes are capable of producing individually or together. The chart is pushed up until a blur is assured, and then the chart is pulled away until the patient can read the smallest line possible.                Accommodative Facility test is designed for determination of the accommodative system flexibility (Flipper Lens Test)—by rapidly alternating the viewing distance under monocular or binocular conditions. The lens flipper with plus and minus lenses is used.        
Negative and Positive Relative Accommodation Test is designed for testing the patient's ability to decrease or increase the accommodation while maintaining convergence.                Special tests were designed for measuring of the Accommodative Convergence/Accommodation Ratio and Convergence Accommodation/Convergence Ratio; both tests are applicable for the training.        
Retinoscopy may be used as well for the accommodative system measuring and training, for example, the Monocular Estimation Method of Dynamic Retinoscopy.
Monocular Estimation Method (MEM) of performing dynamic retinoscopy is an objective method of measuring accommodative lag and checking for accommodative or refractive imbalance at near.
All the aforementioned tests (and a number of similar ones) use the changing of lenses optical power and/or distance to a target in order to measure accommodative (and convergence) system abilities, and all these tests may be used for training the accommodative/vergence systems.
The disadvantage of deploying the enumerated above tests for training the accommodative system is their inconvenience for regular recurrent procedure of training. The known special equipment for accommodation measurements is complicate and expensive. One more inconvenience is the necessity of having an assistant for training.
Therefore, a number of attempts to create special equipment for accommodative system training were undertaken.
The functional background is illustrated in the following description of related art devices.
Slavin invented the “Spinning optics device” (U.S. Pat. No. 4,698,564, Oct. 6, 1987), which creates a specific visual phenomenon in front of one or both eyes of the person wearing the device. In this device, the lenses are constructed by cutting out and affixing stick-on type lens material, such as fresnel prisms, polarizing material, colored filters, cylinder prisms, reflective material, etc., to a plano-plastic disc. A drive motor rotates the rotating lens, which is held in registry with a stationary non-spinning lens by spectacle frames. The direction and speed of the motor are controlled by a digital computer containing a visual training program. The device was intended for visual trainings.
Mateik, et al. patented an “Eye training device” (U.S. Pat. No. 4,756,305, Jul. 12, 1988) for treating such visual disorders as strabismus, amblyopia, myopia, and accommodative insufficiency. The device is shown in FIG. 2—Prior Art attached to the present description. In that device, two images are displayed visually superimposable into a single image and optically conducts one of the images to a right eye viewing port and the other image to a left eye viewing port. The device is intended for enhancing accommodation in a patient.
Randle patented a “Visual accommodation trainer-tester” (U.S. Pat. No. 4,778,268, Oct. 18, 1988) for training a person to control volitionally his focus to his far point from a position of myopia due to functional causes. The perspective view of trainer-tester is shown in FIG. 3—Prior Art. It may be used to measure the accommodation, the accommodation rest position and the near and far points of vision. The device is utilized for various training purposes and test functions by following a series of procedural steps, and interchanging the apertures as necessary for the selected procedure.
Bronskill, et al. teach “Eye exercising devices” (U.S. Pat. No. 4,838,677, Jun. 13, 1989) for positioning the eye along an optical axis, which defines a range of accommodation for the eye. The range of accommodation is bounded by a proximal and a distal limit. An object is movable along the optical path and a displacement device is provided to displace continuously the object along the optical path from a first location on one side of a given one of the limits to a second location on another side of the given limit opposite the first location.
Cushman (U.S. Pat. No. 4,997,269, Mar. 5, 1991) suggested “Scheiner-Principal pocket optometer for self evaluation and bio-feedback accommodation training”—a method and optometer apparatus for measuring the accommodative state of eye of a person and for accommodation training. The optometer apparatus includes: a pinhole aperture plate having a center and a plurality of apertures in the pinhole aperture plate for viewing by the person's eye; a positive lens disposed near the pinhole aperture plate and having an optical axis coincident with the center of the pinhole aperture plate; and scaled means inclined away from the positive lens for indicating to the person the accommodative state of the person's eye in diopters.
Marshall invented a “Device and method for positioning and relaxing accommodation of the eye” (U.S. Pat. No. 5,293,532, Mar. 8, 1994)—apparatus and methods for relaxing accommodation of an eye undergoing examination or other optical or medical procedures while concurrently permitting and facilitating the positioning of a person's subject eye. A patch, cover, or other device designed to occlude and visually stimulate the eye opposite the subject eye includes multiple light sources facing the occluded eye. The practitioner illuminates a selected one (or ones) of the light sources within the patch and directs the patient to fixate on the source. As the occluded eye moves to fixate on the illuminated source, the subject eye follows the movement, thereby repositioning itself. Occluding the eye causes the image seen by it to appear to be at infinity, rather than nearby, causing the ocular muscles of both eyes to relax.
Miyake, et al. patented a “Visual training method and visual training device” (U.S. Pat. No. 7,306,335, Dec. 11, 2007). In a visual training device and a visual training method, different targets are displayed for right and left eyes, respectively, and refractivities of the right and left eyes are measured. Based on the measured refractivities of the eyes, positions of the targets displayed for the right and left eyes are moved in the directions of the respective optical axes. At the same time, the targets are moved so that the visual axes of the right and left eyes incline outward toward the end. The directions of the visual axes of the right and left eyes incline outward toward the end, so that it is possible to relax the strain of musculus ciliaris and relieve visual fatigue through short, effective training.
Yee suggested the “Training enhanced pseudo accommodation methods, systems and devices for mitigation of presbyopia” for and/or treating presbyopia (U.S. Pat. No. 7,413,566, Aug. 19, 2008). Herein, a combination of an alteration to the refractive tissues of the eye with changes in the response of the visual system may be used. The visual system response may include using residual accommodation in a manner similar to that employed by latent hyperopes, a trained response of the pupil, trained psychophysics, or the like. Associated refractive prescriptions may be tailored to take advantage of the subsequent visual system response so as to mitigate presbyopia.
All the aforesaid devices are functionally effective for training the accommodative system, but possess the following disadvantages: equipment/accessories complexity; cumbersomeness; expensiveness; special time/place for training procedure; inconvenience for unaided training (self-training), etc.
In all of the mentioned devices, the main functioning principle remains invariable: alternating the lens optical power and/or distance in order to change the accommodative system strain. The process of changing the strain of eyes is the essence of accommodative system training.
2. Design Background & Related Art
Progressive lenses, or progressive addition lenses (PAL), or varifocal lenses, or multifocal lenses—are corrective lenses used in eyeglasses to correct presbyopia and other disorders of accommodation.
The first patent for a PAL was a British Patent GB15735, granted to Own Ayes with a 1907 priority date. Ayes' patent included the progressive lens design and the manufacturing process. Unlike modern PALs, it consisted of a conical back surface and a cylindrical front with opposing axes in order to create a power progression.
While there were several intermediate steps (H. Newbold appears to have designed a similar lens to Ayes around 1913), Duke Elder developed the world's first commercially available PAL in 1922. This was based on an arrangement of aspheric surfaces.
The first PAL of modern design was a so-called Varilux lens. It was developed by Bernard Maitenaz, patented in 1953, and introduced by the Société des Lunetiers (that later became part of Essilor) in 1959.
Early progressive lenses had relatively crude designs. Modern PALs have gained greater patient acceptance and include special designs to cater to many separate types of wearer application: for example lenses may be customized for use with computers, or to offer enlarged near and intermediate view areas. Over the 1980s through today, manufacturers have been able to minimize unwanted aberrations by improvements in mathematical modelling of surfaces; extensive wearer trials; improved manufacturing and lens metrologic technology.
The design background of present invention is illustrated by the following description of progressive addition lenses (PAL) taught in the related art.
A representative sample of conventional progressive lenses is described in U.S. Pat. No. 4,606,622, Aug. 19, 1986, wherein FueGerhard, et al. (Carl Zeiss) discloses a multi-focal spectacle lens with a dioptric power varying progressively between different zones of vision. Having a short progressive zone, this lens substantially satisfies in the progressive zone as well as in the far-vision and near-vision zones all requirements (monocular and binocular) for sharpness and compatibility, while reducing horizontal and vertical directional errors to tolerable values by selecting distortion on both sides of the principal sight line accordingly.
The very significant PAL parameters are: a progressive corridor length and a progressive corridor width. Wehner, et al. (Rodenstock) patented a double progressive spectacle lens in which a first prescribed progressive surface can be freely designed (U.S. Pat. No. 7,300,153, Nov. 27, 2007). The second progressive surface is then optimized in relation to the first prescribed surface. Thereby, the resulting spectacle lens avoids the need to employ a classic hourglass design progression zone and produces optical and geometric advantages such as an overall height of the progressive lens. In that patent, the use of both internal and external lens sides for progressive surfacing is illustrated.
Guilloux, et al. (Essilor) suggested a method for manufacturing an ophthalmic progressive addition lens with customized design features adapted to a wearer (US Pat. App. 20100079722, Apr. 1, 2010), including a method for determination of a customized ophthalmic progressive addition lens with customized design features. This is one of the most recent samples of freeform surfacing application.
Using the multi-layer technology extended the possibilities of PAL design. Bonnin; Thierry; et al. (Essilor) described an ophthalmic lens that comprises an optical component and a layer placed on its face (US Pat. App. 20080198325, Aug. 21, 2008). The layer has a variable refractive index and is structured so that a second order derivative of the index with regard to a linear spatial coordinate along the face of the optical component is greater than a fixed threshold. The additional layer makes it possible to alter the optical power and astigmatism of the lens with regard to corresponding values only relative to the optical component. For a progressive lens, the additional layer makes it possible to change an addition, a length of progression, and/or a design of the progressive lens.
Nowadays, the complex surfaces of a modern progressive lens can be cut and polished on computer-controlled machines, allowing “freeform surfacing”, as opposed to the earlier casting process.
Since freeform techniques implementation, it has become possible to design and manufacture the multifocal (progressive) lenses of complex surfaces, of customized design. Along with multi-layer technologies, freeform technique defines the modern progressive lenses design limitations. Having regard to these limitations, the customized progressive lens may be ordered from a majority of lens manufacturers (Essilor, Zeiss, Rodenshtock, Hoya, Seiko, Shamir, etc.).
An example of multifocal lenses has been described in U.S. Pat. No. 7,540,610 issued on 2 Jun. 2009 to Carimalo et al: “The invention concerns an ophthalmic lens having a complex surface, with a substantially umbilical meridian and an average sphere progression ranging between 0.50 diopter and 0.75 diopter. The lens is prescribed for esophoric and non-presbyopic users. The lens is prescribed as a standard unifocal lens. Through the presence of the average sphere progression, the user is less adapted to near vision, thus compensating for his/her esophoria”.
The related art is however silent as to employing the multifocal lenses for training the accommodative and vergence systems of a human.